Research and analysis

Wessex water situation: November 2025 summary

Updated 11 December 2025

Applies to England

• Publication for Northern Ireland
• Publication for Scotland
• Publication for Wales

1. Summary

The average rainfall recorded for Wessex during November was 135mm, 128% of the long term average (LTA). There was regular rainfall throughout the month with intervals of dry weather. During Storm Claudia 36% of the month’s rain fell in 4 days. Soil moisture deficit (SMD) decreased throughout November in response to consistent rainfall, but remains below the long term average for this time of year. Monthly mean flows in the chalk catchments were largely normal or below normal, alternatively all other catchments recorded normal or above normal flows. Daily mean flows peaked at most sites around 14 November in response to rainfall recorded during Storm Claudia. Groundwater sites in north Wessex are recording normal levels. Groundwater sites monitoring the chalk are recording notably low and Tilshead is a record exceptionally low for the time of year, but there are signs of recharge with levels stabilised or beginning to increase. Reservoir levels in Wessex have continually increased in November. At the end of the month, reservoir levels for Wessex Water were approximately 69% capacity and combined levels for Bristol Water were 53% capacity.

2. Rainfall

An average of 135mm rain fell across Wessex in November (128% of the LTA). Rainfall occurred regularly throughout November with the wettest period between 11 and 14 October due to Storm Claudia, when 36% of the month’s rain fell. The highest relative rainfall was recorded in the Middle and Upper Bristol Avon which received 151mm rainfall (129% of the LTA). The lowest relative rainfall was recorded in the Purbeck which received 98mm (84% of the LTA).
Over the past 3 months, all hydrological areas in Wessex have received normal or above normal rainfall except for the Little Avon, Lower Bristol Avon and Bristol Frome which received notably high rainfall. Over the past 6 months, all areas in Wessex received normal rainfall. Over the past 12 months, most hydrological areas to the west and north of Wessex received below normal rainfall while most areas to the south of Wessex received normal rainfall. The Brue received notably low rainfall.

3. Soil moisture

Soil moisture deficit (SMD) decreased throughout November in response to recent rainfall. At the end of November SMD for Wessex was between 10-20mm, this is a decrease from 41-70mm recorded at the end of October. Across most hydrological areas in Wessex, the SMD was between 41-70mm. The lowest SMD was recorded in the Little Avon and Lower Hampshire Avon areas at 71-100mm. The difference to LTA is between 6-25mm largely across Wessex.

4. River flows

In November, the majority of sites in the chalk catchments reported normal or below normal monthly mean flows. This is due to low groundwater levels in the chalk aquifer providing limited support to base flow. Outside of the chalk catchments, monthly mean flows recorded normal or above normal due to higher rainfall totals and the groundwater aquifer (Great Oolite and Inferior Oolite) beginning to recharge supporting base flow. Daily mean flows peaked at the majority of sites in Wessex on 14 November in response to the rain from Storm Claudia, however some chalk catchments recorded only normal flows during this period.

5. Groundwater levels   

At the end of November, groundwater sites in Wessex reported between normal and exceptionally low groundwater levels. In the north of Wessex, Wrington (monitoring the Carboniferous Limestone), Didmarton and Allington (both monitoring the Oolite) were recording normal groundwater levels after an increase in groundwater levels during October and November. In the eastern sites on the chalk aquifer (monitoring the chalk in the Upper Hampshire Avon catchment) are reporting notably low or exceptionally low, with levels stabilised or beginning to increase. This is a slow response as this area has received above average rainfall for 3 months, however SMD is still above average and the catchment is recovering from low levels in the summer. In the south of Wessex ground water sites are recording below normal levels with an increase from low levels in October.

6. Reservoir stocks

Both Wessex Water and Bristol Water reservoir levels increased during November. The combined levels at the end of the month for Wessex Water were approximately 69% capacity while for Bristol Water, combined levels were approximately 53% capacity. For Bristol and Wessex Water, this is markedly lower than this time last year.

Author: Wessex Hydrology, Hydrology.Wessex@environment-agency.gov.uk

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use of the information, or reliance upon views contained in this report.